For a chemical reaction A + B ⇌ C + D

($${\Delta _r}{H^\Theta }$$ = 80 kJ mol^$$-$$1) the entropy change $${\Delta _r}{S^\Theta }$$ depends on the temperature T (in K) as $${\Delta _r}{S^\Theta }$$ = 2T (J K^$$-$$1mol^$$-$$1).

Minimum temperature at which it will become spontaneous is ___________ K. (Integer)

An exothermic reaction X $$ \to $$ Y has an activation energy 30 kJ mol^$$-$$1. If energy change $$\Delta$$E during the reaction is $$-$$20 kJ, then the activation energy for the reverse reaction in kJ is ___________. (Integer answer)

3.12 g of oxygen is adsorbed on 1.2 g of platinum metal. The volume of oxygen adsorbed per gram of the adsorbent at 1 atm and 300 K in L is __________.

[R = 0.0821 L atm K^$$-$$1mol^$$-$$1]

The number of significant figures in 50000.020 $$\times$$ 10^$$-$$3 is _____________.